Manufacture of sulfur compounds



Patented Sept. 2, 1947 I 2,426,648 MANUFACTURE or SULFUR com-curiosWalter A. Schulze and Willie W. Crouch, Bartlesville, Okla., assignorsto Phillips Petroleum Company, a corporation of Delaware No Drawing.Application October 19, 1943, Serial No. 506,904

. 1 This invention relates to an improved process for the manufacture oforganic sulfur compounds. In a specific embodiment, this inventionrelates to the direct addition of a compound having the formula RSH, inwhich Rv represents hydrogen or an organic radical substantially inertunder the reaction conditions used, to an ethylenic linkage in anorganic compound, in the presence of a novel catalyst to producemercaptans and/or organic sulfides. A more specific and preferredembodiment involves the manufacture of useful mercaptans from olefinsand hydrogen sulfide through the agency of hydrated boron fluoride, andthe invention will be described in detail with Particular reference tothis embodiment.

The direct synthesis of organic sulfur compounds, especially mercaptansand sulfides (thioethers), by the addition of hydrogen sulfide ormercaptans to olefinic materials, with or without the presence of acatalyst has been reported by various investigators. However, thespecificity of these reactions has not been of the order fre- 1! Claims.(01. 260-609) from the accompanying disclosure and discusquentlydesired, due to the elevated temperatures employed and/ or lack ofactivity or specific action of the catalysts proposed.

An object of this invention is to manufacture catalytically the directvaddition of hydrogen sulfide to aliphatic, substituted aliphatic, andCyclic olefins to yield the corresponding mercaptan derivatives.

Atstill further object of this invention is to provide a process formercaptan manufacture under controlled conditions whereby reactionbetween the selected olefin and hydrogen sulfide can be effected withvirtually no decomposition of the product.

Another object ofthis invention is to manufacture mercaptans fromolefinic hydrocarbons and hydrogen sulfide at mild conditions oftemperature and pressure in the presence of a liquid hydrated boronfluoride catalyst.

Further objects and advantages of the invention will be apparent, to oneskilled in the art,

ing the addition of H25 to olefins.

sion.

We have discovered that the sulfur-compoundforming reactions referred toabove are smoothly and efficiently accomplished under exceptionally mildconditions under the catalytic influence of hydrated boron fluoride.Since the catalyst of this invention is very active, it may be appliedat relatively low temperatures to a great variety of olefinic materialsto ive the desired correspondingsulfur compounds with a minimum ofundesirable secondary reactions. I

Our novel and active catalyst may be applied to the reaction betweenmercaptans and olefinic hydrocarbons to produce sulfides. be applied tothe reaction between H28 and olefins to produce mercaptans as hereindiscussed. While in the latter reaction some formation of sulfides maybe expected due to a secondary reaction between the product mercaptanand'the olefin or to other factors, it has been found in practice thatsuch sulfide formation may be kept to a desired low and even negligiblevalue by maintaining 'a substantial excess of H28 in the reaction zoneand/or by operating at moderate temperatures which are still adequatefor effect- On theother hand, when it is desired to produce sulfides asthe product of an olefin-H28 reaction, the, yield of sulfides may bematerially increased by suitable control of reaction conditions, as byoperating with higher olefinzHzS ratios. In any case, the activity ofour catalyst makes possible the carrying out of the chosen reactionunder moderate conditions which enable control of product to anexceptionally advantageous degree.

The process of the present invention in preferred embodiment comprisesthe contacting of controlled proportions of olefinic hydrocarbon, ormixtures of olefinic hydrocarbons, and hydrogen sulfide or mercaptanwith a liquid boron fluoride hydrate catalyst under conditions selectedto produce a substantial conversion of olefin to the correspondingmercaptan or sulfide, as the case may be. For example, in the use of themercaptanforming reaction, the hydrocarbon-hydrogen sulfide blend may becontinuously contacted with products and returned to the contactingzone. The product layer may be continuously with drawn from the catalystseparator for processing by suitable stabilization and distillationsteps.

It may also .3 Alternatively, the reaction may be carried out in a batchoperation with intermittent injection of feed into the contacting zoneand intermittent withdrawal and subsequent processing of the productstream. In many instances, the incorporation of a diluent comprisingpure non-olefinic hydrocarbons, such as n-pentane or fractions ofnatural or straight-run gasoline, may be advantageously utilized incontrolling the reaction temperature and in maintaining a favorablehydrogen sulfide-olefin mol ratio without resorting to excessivepressures. In-instances where mercap tan of high molecular weight andhigh viscosity are involved, the presence of a low viscositydiluentgreatly aids in the catalyst separation step.

In a specific preferred embodiment of the invention, a C12-C14 olefinmixture derived from the catalytic polymerization of C: and C4 refineryolefins is employed, in admixture with about 80 per centn-pentane, asthe hydrocarbon feed'to the reaction. Enough hydrogen sulfide is addedto the hydrocarbon mixture to give an HzS-olefin .iol ratio of fromabout two to about five. The resulting composite mixture, under apressure of about 100 to 500 pounds per square inch gage, is theninjected into a reaction zone where intimate contacting of feed andcatalyst is accomplished by suitable means. For this particular system,the reaction temperature may be maintained between about 40 and 50 F.,for optimum results, although higher and lower temperatures areoperable. An emulsion of catalyst and product is continuously dischargedinto a catalyst separator, from which the product stream is withdrawn ata rate adjusted to give a reaction time of about 15 to 20 minutes. Thecatalyst separates by gravity in the separator and is continuouslyreturned to the reactor. The product stream is stripped of its excessH2S and pentane diluent, and the resulting high-boiling material isdistilled under reduced pressure to separate unreacted olefin from themercaptan product.

The catalyst composition of the present invention is convenientlyprepared by passing gaseous boron fluoride into water until thedesired'hydrate concentration is realized. During the solution of BE! inwater, considerable heat is evolved and suitable means for coolingshould be provided. Since the specific gravity of a completely saturatedsolution, is approximately 1.77, convenient control of concentration canbe effected by means of hydrometer determinations. The combination ofwater and boron fluoride may be carried out at atmospheric pressure orin a closed vessel at pressures of from 100 to 1000 pounds per squareinch or higher. In either case the quantity of BF: taken up whencomplete saturation is effected corresponds substantially to one mol' ofBFa per mol of Water. Catalyst formation under pressure is, however,more convenient and much less time-v consuming. The catalyst preferablyemployed is water substantially saturated with BFa, that is themono-hydrate BF:H2O; however, an excess of water may be used to give anydesired BF3-H2O mol ratio.

Maximum activity of the boron fluoride hydrate catalyst of thisinvention is ordinarily realized when the moi ratio of water to boronfluoride falls within the range of about 1.5:1 to about 1:1, althoughratios as high as 2:1 may often be used. The exact composition of thecatalyst phase and its mode of action are not entirely understood, sincecomposition changes occur during the reaction. We have found thatmercaptans can be dissolved in boron fluoride hydrate With the evovolumeof original catalyst charge, the volume of catalyst phase has increasedby an increment equal to about 0.5 to 0.75 of the original volumecharged. This volume increase is not as great as observed with puremercaptan and new catalyst, hence it is concluded that the H28 contentof the system and the diluent when employed may operate to preventexcessive solution of product mercaptans in the catalyst phase.

In the production of mercaptans with the above catalyst and by thehereinbefore described pro cedure, it is necessary to maintain a molalexcess .of hydrogen sulfide relative to the olefin content of the feedin order to favor the mercaptan reaction and to suppress undesirablepolymerization and/or depolymerization of the olefin. Satisfactoryreaction mixtures may have Has-olefin mol ratios of from about one toabout six, with intermediate values of about two to about five beingpreferred.

The employment of a diluent in the reaction feed, while not mandatory,is often found to be advantageous. Where the manufacture of highmolecular-weight mercaptans is involved, the use of a diluent affords aconvenient means of maintaining the moderate temperaturesv required toprevent fragmentation of the primary product mercaptan. A furtheradvantage derived from the use of a diluent liquid is the reduction ofviscosity of high molecular-weight products, thus facilitating catalystseparation and effecting general improvement in the fiow characteristicsof the charge and product streams. The employv ment of diluents alsofavors the maintenance of favorable HzS-olefin moi-ratios in the feedwithout'the necessity of resorting to excessively high pressures.Saturated hydrocarbons are ordinarily preferred as diluents, and areusually selected from narrow-boilingerange fractions of natural orstraight-run gasoline. The diluents may be selected on the basis oftheir ease separation from the product mercaptans. The

With high-boiling mercaptans, a diluent such a. n-pentane might beselected, whereas in the production of ethyl mercaptan a 200- 250 F.fraction of natural gasoline would be satisfactory. The mount of diluentemployed will obviously depend on any or all of the factors previouslymentioned,

and may vary from 10 to 90 volume per cent of the hydrocarbon feed.

Because of the high degree of activity displayed by the catalystcompositions of this invention, moderate reaction temperatures may beemployed with a wide variety of olefin reactants.

Substantially atmospheric temperatures, such as those ranging from about32F. to about 150 F.

action pressures are largely determined by thevolatility of the olefin,the H28 concentration, and the quantity of diluent employed. With thecatalyst of this process, liquid phase operation is especiallydesirable, and sufficient pressure and diluent are usually employed inorder to fulfill this condition. Thus pressures of from about 100 poundsgage to 1000 pounds or more are ordinarily adequate.

The flow rate of feed to the reaction zone is selected to conform withcatalyst activity, the nature of the olefinic component, and the desireddepth of conversion. In order to obtain an olefin conversion of 80 percent or more per pas with an active catalyst, the olefin feed rate,expressed independently of the H28 and diluent, may range from about 0.5to about 5 liquid volumes per volume of catalyst per hour.

The olefinic hydrocarbons which may be reacted with hydrogen sulfide incarrying out this invention are those containing at least one ethylenicbond, and include aliphatic olefins, cyclic olefins, and substitutedaliphatic and cyclic olefins in which the substituting group or groupsmay be hydrocarbon or non-hydrocarbon radicals of such character thatthey do not interfere with the primary reaction. I

In order to further illustrate the specific uses and advantages of thepresent invention, the following exemplary operations will be described.However, since these and numerous other process modifications-will beobvious in the light of the foregoing disclosure, no undue limitationsare intended.

Example I Ethyl mercaptan was prepared from ethylene and hydrogensulfide in the presence of boron fluoride hydrate. The catalyst wasprepared by bubbling gaseous BF: through a body of water held in an icebath until no more BFa could be absorbed. The hydrate so preparedcorresponded approximately to the empirical formula BFxHzO. In order towork under liquid phase conditions, the feed to the reactor was preparedwith an inert diluent comprising a 200-250 F. fraction of naturalgasoline. The feed blend was made up to give an HzS-ethylene mol ratioof two, and the final composition in per cent by weight was as follows:hydrocarbon diluent, 56.7; ethylene, 14.2; hydrogen sulfide, 29.1. Thismixture was continuously charged to a turbo-mixer type reactorcontaining the catalyst under a pressure sufiicient to maintainliquid-liquid contacting in the reactor. The reaction conditions arelisted herewith: i

H2S-C2H4, mol ratio 2 Feed-catalyst, volume ratio 3 Contact time,minutes 32 Temperature, F. 130-135 Pressure, p. s. i, g 800 The contentsof the reactor in the .form of an emulsion were continuously dischargedinto a catalyst separator from which the mercaptanhydrocarbon layer wascontinuously removed while the separated catalyst phase was returned tothe contacting zone. The excess B28 was removed from the accumulatedproduct stream in a stabilizing operation, and the ethyl mercaptan wasfractionally distilled from the hydrocarbon diluent. At the conclusionof the operation the catalyst was still active. The ethyl mercaptanrecovered represented a yield of about 65 per cent of theory ascalculated on the weight of ethylene charged. The product mercaptanrecovered was equivalent to about pounds per pound of catalyst charged.

Example II The specificity and activity of saturated boron fluoridehydrate toward the olefin-H28 reaction were tested under the unfavorableconditions of a moderate atmospheric temperature and atmosphericpressure and low H to olefin mol ratio. The reaction was carried outwith a continuous contacting procedure with a glass reaction vesselequipped with a mechanical stirrer and catalyst separator. A blendcontaining 10 volume per cent of commercial diisobutylene in cyclohexanewas pressured to 60 p. s. i. with. hydrogen sulfide to prepare the feed.The following conditions were employed in effecting the reaction:

Total diisobutylene charged, ml 300 HzS-olefin,'mol ratio 1.3Feed-catalyst, volume ratio 2 Reaction time, minutes 30 Temperature, F.76 Pressure Atm.

After removal of the diluent and unreacted olefin.

the yield of Ca mercaptans amounted to 205 ml. The catalyst volumeincreased from to ml. during the reaction. The catalyst-soluble materialwas found to be substantially alkyl sulfides.

Example III A C12Cl4 fraction of olefins derived from the catalyticpolymerization of refinery light olefins was converted to mercaptans ina continuous operation under pressure. A blend of 20 weight per cent ofthe olefinic material in n-pentane was prepared, and sufficient H2S wasadded .under pressure to give a substantial molal excess over theolefin. This blend was continuously passed through the reaction zonecontaining boron fiuoride mono-hydrat under the conditions listed below:

Hrs-olefin, mol ratio 2.8 Feed-catalyst, volume ratio 4.6 Reaction time,minutes 20 Temperature, F 75-80 Pressure, p. s. i. g 200 Cyclohexylmercaptan was prepared from a blend of about 20 volume per centcyclohexene in n-pentanetogether with sufiicient H28 to give a molalexcess over the olefin present. The feed blend was passed continuouslythrough a 700 ml. turbo-mixer type reactor, charged with 150 ml. of

boron fluoride hydrate prepared as in Example I,

under the following conditions:

HzS-olefin, mol ratio 4.4 Reaction time; minutes 20 Temperature, F100-105 Pressure, p. s. i. g 350 The catalyst was continuously recycledto the reaction zone while the hydrocarbon-product blend purityifications, it will be appreciated that the process may be effected inmanners other than those described. Various alternative operations willbe apparent to one skilled in the art in view of the instant disclosure,and the invention is accordingly to be limited only by the accompaningclaims. a

We claim:

1. In the formation of organic sulfur com- 1 pounds by the catalyticaddition of a compound selected from the group consisting of hydrogensulfide and mercaptans to an olefin, the improvement which comprisesconducting said addition reaction in the presence of a liquid catalystcomplex comprising boron fluoride and water and having a waterzBFs molratio within/the range of about 2:1 to about 1:1.

2. A process for the formation of organic sulfur compounds whichcomprises contacting an olefinic hydrocarbon with hydrogen sulfide inthe presence of a liquid catalyst formed by bringing together boronfluoride and water in such proportions as to form a catalyst in whichthe mol ratio of water to boron fluoride is within the range of about1.5:1 to about 1:1, under conditions such that an addition of hydrogensulfide to the olefinic hydrocarbon takes place.

3. A process which comprises contacting an olefinic hydrocarbon withhydrogen sulfide in the presence of water saturated with boron fluorideunder conditions such that the addition of hydrogen sulfide to theolefinic hydrocarbon takes place.

4. The process of claim 3 in which reactants,

are maintained substantially in'liquid phase. r

5. A process for producing a mercaptan which,

comprises contacting an olefinic hydrocarbon water having a waterzBFsmol ratio within the range of about 2:1 to about 1:1 at a temperaturewithin the range of about 32 F. to about 150 F. under conditionsefiecting the addition of hydrogen sulfide to the olefinic hydrocarbonas the principal reaction of the process.

8. The process of claim '7 in which a hydrogen sulfideto olefinichydrocarbon mol ratio greater than one is maintained.

9. The process of claim 3 in which said olefinic hydrocarbon is analiphatic monoolefin.

10; The process ofclaim 3 in which said ole finic hydrocarbon isethylene.

11. The process of claim 3 in whichsaid olefinic hydrocarbonis acyclo-olefin.

12. The process of claim 3 in which saidole- 'finic hydrocarbon iscyclohexene.

13. A process for producing'high-boiling me1 captans which comprisesseparating from eifiuents of an olefin polymerization process an olelfinic hydrocarbon fraction essentially comprising olefins-having from 12to 14 carbon atoms per molecule; contacting said fraction together witha liquid saturated hydrocarbon diluent and by drogen sulfide, undersufiicient pressure to dissolve in the liquid reaction mixture a molarexcess of hydrogen sulfide relative to the olefins about 1.521 to about1:1 at a temperature within I the range of about 32 F. to about 150 F.for a gen sulfide in the presence of a liquid catalyst comprisingeffective amounts of boron fluoride hydrate complex in which the'molratio'of water to boron fluoride is within the rangeof about 2:1 toabout 1:1 under conditions eifecting th condensation reaction betweenhydrogen sulfide and the olefinic hydrocarbon to produce the mercaptan.

6. A process for producing mercaptans which compri'sescontacting anolefin with hydrogen' sulfide in the presence of a catalyst essentially7 comprising hydrated boron fluoride in the form of a liquid complexhaving a waterzBF: mol ratio within the rang of about 1.5:1 to about 1:1at a temperature within the range of 32 F. to 150 F. under conditionsefiecting the condensation reaction between hydrogen sulfide andthe.olefin to produce a mercaptan.

7. A process for producing mercaptans which comprises contacting anolefinic hydrocarbon with hydrogen sulfide in admixture with an inertliquid hydrocarbon diluent in the presence of a liquid catalystcomprising effective amounts of an addition compound of boron fluorideand .file of this patent:

time such as to efiectsubstantial addition of hydrogen sulfide toolefins, and recovering a mercaptan fraction comprising mercaptans soproduced having from '12 to 14 carbon atoms per molecule.

14. A process for producing high-boiling mercaptans which comprisescontacting an olefin of from 12 to 14 carbon atoms per molecule withhydrogen sulfide at a temperature within the range, of about 32 F. toabout F. in the presence of. a catalyst consisting of a liquid complex'of boron ,fiuoride and water having a water'zBFs mol ratio within .the 1range of about .2::1 to"about 1:1, therbyfproducing amercapt'an w havingfrom 12 to'14; carbon atoms per-molecule asthe principalproduct offtheprocess WALTER A.

WILLIE w. CROUCH.

' REFERENCES CITED The following references are of record in the

